US1957949A - Antenna - Google Patents

Description

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I ANTENNA Filed July 11, 1929 I293 F 2 I 49 5 E 91 Y Egg; I 6

CHARLES SAMUEL FRANKUN AND ERNEST REE ATTORTNEY Patented May 8, 1934 UNITED STATES PATENT OFFICE ANTENNA poration of Delaware Application July 11, 1929, Serial No. 377,419 In Great Britain July 17, 1928 10 Claims. (01. 250-33) This invention relates to antennae or aerials for use in wireless telegraphy and telephony, and more particularly to aerials for use in directive aerial systems.

In prior British specifications Nos. 242,342 and 285,106 are described aerials which are long relative to the wave length employed, and in which radiation from alternate half wave lengths is wholly or in part suppressed, whereby improved directional qualities in a direction at right angles to the length of the aerial are obtained. The present invention has for its principal object to provide an aerial having strongly marked directional qualities, and in which these qualities shall be obtained without any substantial suppression of radiation.

According to this invention an aerial, which is long relative to the wave length employed, is substantially reversed in direction at alternate half wave lengths, the arrangement being such that the radiation from these alternate half wave lengths is added to that of the remaining half wave lengths.

In one form of construction, a vertical aerial is formed with its first or lowest half wave length as a simple vertical wire. The second half wave length proceeds for a distance equal to .1 of a Wave length as a prolongation of the first half wave length, after which it turns through a right angle and proceeds in a perpendicular direction for .05 of a wave length. It is then bent through a second right angle and extends downwardly through .2 of a wave length, after which it turns through a third right angle, proceeding in a direc-' tion perpendicularly away from the first half wave length through a further .05 of a wave length. Finally, it is bent again through a right angle and proceeds upwardly through its final .1 of a half wave length. The third half wave length is formed as a vertical prolongation of the last portion of the second half wave length. The fourth half wave length is formed similarly to the second, except that it proceeds towards the vertical line, in which the first half wave length lies, instead of away from it; in other words, the second and fourth hali wave lengths are symmetrical about a line perpendicularly bisecting the third half wave length.

The fifth half wave length is a vertical straight wire in line with the first, and vertically above it; the sixth half wave length is similar to the sec ond and is vertically above it part for part; the seventh half wave length is a straight line in line with the third and vertically above it; the eighth half wave length resembles the fourth and lies vertically above it part for part, and. so on for any desired number of half wave lengths.

It is to be understood that in the preceding description the term half wave length means the distance along the wire travelled by the wave during half a period of oscillations.

Aerials in accordance with this invention may be employed vertically, horizontally or at any desired angle. In use they may be earthed at one end through a resistance equal to the surge impedance of the wire, so as to prevent reflection from that end, or alternatively, reflection may be prevented by employing the arrangement .set forth in British specification No. 281762.

By making the length of the wire between centres of adjacent sections of the aerial greater or smaller than half a wave length, a progressive change of phase between sections may be obtained. Maximum radiation may thus, if desired, be obtained in directions substantially'difierent from the direction at right angles to the general direction of the aerial.

Aerials in accordance with this invention are adapted for use in combination to form so-called beam aerial systems, and may, of course, be employed either with or without reflecting systems which maybe erected vertically, horizontally or at any other desired angle appropriate to circumstances.

The invention is illustrated in and explained in connection with the accompanying diagrammatic drawings, in which Figure 1 shows an aerial in accordance with the invention contained in-British specification No. 242,342, while Figures 2 to 7 show aerials in accordance with the present invention. a

In all the figures the aerials are presumed to be fed from the end X (the bottom), and in each aerial the centres of the half wave lengths are indicated at A B C D and so on, i. e. when currents at correct operating frequencies are fed into the end X of an aerial, there will be currents of equal phase in the parts whose centres are at B D F etc. the phase of the latter currents being opposite to that of the former currents. The travelling wave in an aerial will normally be reflected from the upper end Y, and, assuming correct terminal conditions, the reflected wave will be in phase with the forward wave at the points A B C D etc. and will produce a standing wave in the wire. This reflected wave, which will be weaker than the forward wave owing to loss by radiation, may, if desired, be eliminated, for example, by means of an absorption circuit such that the impedance at the end Y of an aerial is made equal to the surge impedance of the wire.

The field at a distance in a direction at right angles to the length of the wire, and due to the travelling wave in any half wave section of the aerial, is the same as would be produced by a standing wave in each half section having a maximum value at the centre equal to the maximum value of the travelling wave. This is indicated in the diagrams by the dotted curves which show in conventional schematic form the equivalent standing waves.

The function and operation of-the various arrangements shown in the accompanying drawing will; it is thought, be readily appreciated from a consideration of the foregoing. In all the figures the aerials are about two wave lengths in linear extension.

In Figure 1, which shows an aerial as described in prior British specification No. 242,342, there are seven half wave lengths of wire, the sections having their centres at A C E and G being radiating sections, and the other sections being formed nonradiating. Since there are four radiating sections, all in phasewith respect to currents causing radiation in a direction at right angles to the aerial as a whole the resultant field may be regarded as having a value of four arbitrarily chosen units.

In Figure 2, which shows an arrangement in accordance with the present invention, there are still seven half wave sections, but the sections B D and F instead of being non-radiating are caused to radiate, and, owing to the reversal of the direction of the wire, the radiation therefrom for the most part assists the radiation from the sections A C E and G. If the aerial shown in Figure 2 be energized with currents equal to those with which the aerial shown in Figure 1 must be energized to obtain four units of field strength in a direction at right angles to the aerial, the said aerial shown in Figure 2 will give approximately 5.2 units of field strength in the same direction.

Figures 3, i and 5 show modifications of the arrangement shown in Figure 2, in which the amount of wire reversed in direction is increased.

Whereas in Figure 2 the amount of wire reversed in each alternate half wave length section is .2 of a wave length, in Figure 3 the amount reversed is .24 of a wave length; in Figure 4 the amount reversed is .28 of a wave length; and in Figure 5 the amount is .32 of a wave length. This increase of the amount of wire reversed not only reduces the linear extension of an aerial for a given number of wave lengths of wire, but also increases the radiation from the alternate half wave lengths. Thus the field strengths ob- 'tained from the aerials shown in Figures 3, 4 and 5 under the same conditions for obtaining a field strength of four units from the arrangement shown in Figure l, are respectively 7.25; 9.5 and 11.275.

The arrangement schematically illustrated in Figure 5 may conveniently be embodied in practice by making the aerial in the form of a vertically extending hexagonal cage-like structure, the connecting wires n n1 and m m1 being equal in length to cross wires, such as 10 pl.

It will be appreciated that the increase in the number of wave lengths of wire for a given linear extension of aerial results in an increased radiation per unit over all length of aerial.

For any specified linear dimension of aerial, the construction may be such that the major part of the energy fed in at X is radiated before the end Y is reached and the wave reflected from Y may thus be made very weak-indeed, if a reflection absorbing device such as resistance 2 shown in Fig. 5 be provided as above set forth, the reflected wave may be substantially entirely eliminated and the loss of energy involved be made very small indeed. Furthermore the radiation per unit linear length of the aerial in different parts thereof may be controlled by progressively varying along the aerial the amount of wire reversed in each alternate half wave length, so that it is possibie to a large extent to compensate for the natural decrement of the current along the aerial and obtain an aerial of substantially uniform radiation per unit length, by progressively increasing the amount of reversal in alternate half wave lengths towards the top of the aerial. Figure 7 shows a modification of this kind in which sections B, D and F constitute reversals of progressively increasing amount. Any other distribution may, of course, be obtained if desired-for example, the radiation per unit linear length may be made greatest at the centre portion of the aerial.

If desired multiple wires in parallel may be employed in place of single wires or a combination of sin le wires and multiple wires in parallel may be employed.

Figure 6 shows a modification of this kind, in which the sections A, C and E are formed of cages, the reversed sections 13 and D being constituted by single wires.

We claim as our invention:

1. An antenna comprising a first straight linear radiating section one half wave length long, a second straight linear radiating section one half wave length long parallel to and extending in the same general direction as said first section, and an intermediate radiating half wave length long section directly connecting together both said first two radiating sections, the greater portion of said intermediate radiating section being parallel to said first section, but reversed in direction whereby radiation from said intermediate section is caused to be additive to that from the tother two sections in a specifically desired direcion.

2. An antenna comprising a first straight linear section a half wave length long, a second straight linear section a half wave length long parallel to and extending in the same general direction as said first section, an intermediate radiating half wave length long section directly connecting together both said first two sections, the greater portion of said intermediate section being parallel to said first section, but reversed in direction with respect thereto, a third straight linear radiating section one half Wave length long and extending in the same general direction as said first two linear sections, and another intermediate radiating section a half Wave length long similar to said first mentioned intermediate radiating section directly connectingtogether said second and third straight linear sections whereby radiation from said intermediate half wave length long section is caused to be additive to that from the other straight linear sections in a specifically desired direction, the amount of reversal of said two intermediate sections being different whereby substantially uniform radiation per unit length or" said antenna is obtained.

3. An antenna in accordance with claim 1, characterized in this, that at least one of the half wave sections comprises a plurality of conductors in parallel.

4. An antenna in accordance with claim 1, characterized in this, that alternate half wave length sections are each composed of a plurality of conductors in parallel, said alternate half wave length sections being joined in series by partly reversed single conductors each a half wave length long.

5. An aerial as claimed in claim 1 and in which alternate half wave lengths are constituted each by a plurality of conductors in parallel, said half wave lengths being joined in series by partly reversed single conductors each a half wave length long, substantially as described.

6. An antenna in accordance with claim 1, characterized in this, that the antenna consists of a single conductor formed into a polygonal cage-like structure.

7. An antenna comprising a first straight linear radiating section one half wave length long, a second straight linear radiating section one half wave length long parallel to and extending in the same general direction as said first section, and an intermediate radiating half wave length long section directly connecting together both said first two radiating sections, the greater portion of said intermediate radiating section being parallel to said first section, but reversed in direction whereby radiation from said intermediate section is caused to be additive to that from the other two sections in a specifically desired direction, and an absorptive arrangement for substantially eliminating waves reflected from the end of the antenna.

8. An antenna comprising a plurality of half Wave length conductors, one of which is maintained linear, and, a half wave length conductor serially connected to said linear half wave length conductor, said serially connected conductor extending first in the same direction as said first mentioned linear conductor, then extending at right angles thereto, then extending parallel to but in a reverse direction relative to said linear conductor, then extending in a direction perpendicular to its reversed direction and then extending for the remaining portion of the half wave length in the same general direction as and parallel to the first mentioned half wave length linear conductor.

9 An antenna comprising a plurality of half wave length conductors, one of which is maintained as a straight, linear conductor, and another of which is a half wave length conductor serially connected to said first linear half wave length conductor, said serially connected conductor extending first as a prolongation of the first conductor for a distance equal to .1 of a wave length, after which it turns through a right angle and proceeds in a perpendicular direction for .05 of a wave length, then extending through a second right angle for a distance of .2 of a wave length parallel to but in a reverse direction relative to said linear conductor, after which it turns through a third right angle proceeding in a direction perpendicularly away from the first half wave length linear conductor through a further .05 of a wave length, and finally extending in a direction perpendicular to said .05 wave length portion and in the same general direction as and parallel to the first mentioned half wave length linear conductor for the remaining portion of the half wave length.

10. An antenna comprising a first straight linear radiating section substantially one half wave length long, a second straight linear radiating section also substantially one half wave length long parallel to and extending in the same general direction as said first section, and an intermediate radiating section one half wave length long directly connecting together both said first two radiating sections, portions of said intermediate radiating sections extending as prolongations of said first and second sections, and another portion of said intermediate section being reversed in direction with respect to said first and second linear sections whereby radiations from said intermediate section is caused to be additive to that from the other two sections in a specifically desired direction.

CHARLES SAMUEL FRANKLIN. ERNEST GREEN.

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